Buck-boost DC converter

Abstract

The application discloses a boost-buck DC converter, one end of a first flying capacitor is connected with one end of an inductor, and a connection node is connected to a voltage input end through a switch network and grounded through the switch network, the other end of the first flying capacitor is grounded through the switch network and connected to the voltage input end; one end of a second flying capacitor is connected with the other end of the inductor, and the connection node is connected to a voltage output end through the switch network, the other end of the second flying capacitor is grounded through the switch network and connected to the voltage output end; the switch network switches a first state, a second state and a third state in turn in each switching cycle, and the first flying capacitor and / or the second flying capacitor are connected in parallel with the inductor in at least two states, hard charging is performed, the hard charging time is prolonged, the inrush current is small, the current on the inductor is reduced, the loss is reduced and the device can be protected.

Description

Technical Field

[0001] This invention relates to the field of voltage converter technology, and more specifically to a buck-boost DC-DC converter. Background Technology

[0002] With the continuous development of power electronics technology, buck-boost DC-DC converters are widely used in various electronic devices. These converters transform the DC voltage output from the power supply to the required DC circuit. In some applications, multiple high-efficiency power supplies may be required (e.g., a display requires 3.4V, an I / O subsystem requires 1.8V, and the core processor requires 1V). Therefore, compared to traditional inductor converters, hybrid buck-boost DC-DC converters constructed with flying capacitors have been proposed to improve voltage conversion efficiency.

[0003] Currently, common buck-boost DC-DC converters include multi-mode hybrid buck-boost DC-DC converters. When a multi-mode hybrid buck-boost DC-DC converter is working, it operates in two phases. That is, within one working cycle, the multi-mode hybrid buck-boost DC-DC converter has two operating states. In one operating state, it can perform hard charging of the flying capacitor. When only one operating state is used to hard charge the flying capacitor, under extreme VCR (Voltage Conversion Ratio) conditions, the hard charging time may be short, resulting in a large inrush current, which increases losses and may damage the device. Summary of the Invention

[0004] The main technical problem solved by this invention is that hybrid buck-boost DC-DC converters with only one operating state for hard charging of flying capacitors may have a short hard charging time under extreme VCR (Voltage Conversion Ratio) conditions, resulting in large inrush current, increased losses, and potential damage to the device.

[0005] One embodiment of this application provides a buck-boost DC-DC converter, comprising:

[0006] The voltage input terminal is used to connect the input voltage output from an external voltage source;

[0007] The voltage output terminal is used to provide the output voltage to the connected load.

[0008] The voltage conversion module includes a first flying capacitor, a second flying capacitor, an inductor, and a switching network;

[0009] One end of the first flying capacitor is connected to one end of the inductor, and the connection node is connected to the voltage input terminal and grounded through the switching network. The other end of the first flying capacitor is grounded and connected to the voltage input terminal through the switching network.

[0010] One end of the second flying capacitor is connected to the other end of the inductor, and the connection node is connected to the voltage output terminal through the switching network. The other end of the second flying capacitor is grounded and connected to the voltage output terminal through the switching network.

[0011] The switching network is used to receive a drive signal and, in response to the drive signal, sequentially switch between a first state, a second state, and a third state in each switching cycle; in at least two of the first state, the second state, and the third state, the first flying capacitor and / or the second flying capacitor are connected in parallel with the inductor to reduce the current on the inductor.

[0012] In one embodiment, in the first state, the connection node of the first flying capacitor and the inductor is connected to the voltage input terminal through the switching network and disconnected from ground; the other end of the first flying capacitor is grounded through the switching network and disconnected from the voltage input terminal; the connection node of the second flying capacitor and the inductor is connected to the voltage output terminal through the switching network; the other end of the second flying capacitor is grounded through the switching network and disconnected from the voltage output terminal.

[0013] In the second state, the connection node of the first flying capacitor and the inductor is disconnected from the voltage input terminal and ground. The other end of the first flying capacitor is connected to the voltage input terminal through the switching network and disconnected from ground. The connection node of the second flying capacitor and the inductor is connected to the voltage output terminal through the switching network. The other end of the second flying capacitor is grounded through the switching network and disconnected from the voltage output terminal.

[0014] In the third state, the connection node of the first flying capacitor and the inductor is grounded through the switching network and disconnected from the voltage input terminal. The other end of the first flying capacitor is disconnected from the voltage input terminal and ground. The connection node of the second flying capacitor and the inductor is disconnected from the voltage output terminal. The other end of the second flying capacitor is connected to the voltage output terminal through the switching network and disconnected from ground.

[0015] In one embodiment, the first state lasts for a preset duration.

[0016] In one embodiment, the switching network includes: a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, and a seventh switch;

[0017] One end of the first switch is connected to the voltage input terminal and one end of the second switch; the other end of the first switch is connected to one end of the fourth switch, one end of the inductor, and one end of the first flying capacitor; the other end of the second switch is connected to the other end of the first flying capacitor and one end of the third switch; one end of the fifth switch is connected to the other end of the inductor and one end of the second flying capacitor; one end of the sixth switch is connected to the other end of the second flying capacitor and one end of the seventh switch; the other end of the sixth switch is connected to the fifth switch and the voltage output terminal; the other ends of the third switch, the fourth switch, and the seventh switch are grounded.

[0018] When the first switch, the third switch, the fifth switch, and the seventh switch are in the ON state, and the second switch, the fourth switch, and the sixth switch are in the OFF state, the switch network is in the first state;

[0019] When the second switch, the fifth switch, and the seventh switch are in the ON state, and the first switch, the third switch, and the sixth switch are in the OFF state, the switch network is in the second state;

[0020] When the fourth and sixth switches are in the ON state, and the first, second, third, fifth, and seventh switches are in the OFF state, the switch network is in the third state.

[0021] In one embodiment, the second switch, the fourth switch, the fifth switch, the sixth switch, and the seventh switch are all transistors.

[0022] In one embodiment, the first switch and the third switch are MOS transistors with integrated dynamic body selectors.

[0023] In one embodiment, the buck-boost DC-DC converter further includes:

[0024] A voltage control module is connected to the voltage output terminal and the switching network. The voltage control module is used to generate the drive signal according to the output voltage and the preset reference voltage, so that the switching network sequentially switches the first state, the second state and the third state in each switching cycle, and the first state lasts for the preset duration.

[0025] In one embodiment, the voltage control module includes: a compensation circuit, a sawtooth wave generator, a first comparator, a second comparator, a three-phase generator, and a drive signal generation circuit;

[0026] The input terminal of the compensation circuit is connected to the voltage output terminal, and is used to amplify the output voltage and compensate for the frequency to generate a first voltage signal.

[0027] The sawtooth wave generator is used to generate sawtooth wave signals and clock signals;

[0028] The first comparator is used to acquire the sawtooth wave signal and the preset reference voltage, and generate a first comparison signal characterizing the comparison result between the sawtooth wave signal and the preset reference voltage;

[0029] The second comparator is used to acquire the first voltage signal and the sawtooth wave signal, and generate a second comparison signal characterizing the comparison result between the sawtooth wave signal and the first voltage signal;

[0030] The phase generator is used to receive the first comparison signal, the second comparison signal and the clock signal to generate a reference clock signal and output it to the drive signal generation circuit;

[0031] The drive signal generation circuit is used to generate the drive signal in response to the reference clock signal.

[0032] In one embodiment, the compensation circuit is a type-three compensation circuit.

[0033] In one embodiment, the voltage conversion module further includes:

[0034] An output capacitor is connected between the voltage output terminal and ground to stabilize the output voltage.

[0035] According to the buck-boost DC-DC converter of the above embodiment, since the flying capacitor (first flying capacitor and / or second flying capacitor) is hard-charged in both states of the switching network, that is, the flying capacitor (first flying capacitor and / or second flying capacitor) can be hard-charged in both operating states of the buck-boost DC-DC converter, the hard-charging time is extended, the surge current is reduced, the current on the inductor is reduced, the loss is reduced, and the device can be protected. Attached Figure Description

[0036] Figure 1 This is a circuit diagram of a multi-mode hybrid buck-boost DC-DC converter in the prior art;

[0037] Figure 2 The circuit structure diagram of a single-mode large inductor current hybrid buck-boost converter in the prior art is shown.

[0038] Figure 3 This is a circuit diagram of a buck-boost DC-DC converter according to one embodiment;

[0039] Figure 4 This is a state diagram of a buck-boost DC-DC converter when the switching network is in a first state, according to one embodiment.

[0040] Figure 5 This is a state diagram of a buck-boost DC-DC converter when the switching network is in the second state, according to one embodiment.

[0041] Figure 6 This is a state diagram of a buck-boost DC-DC converter when the switching network is in the third state, according to one embodiment.

[0042] Figure 7 A detailed circuit diagram of a buck-boost DC-DC converter according to one embodiment;

[0043] Figure 8 This is a circuit diagram of a phase generator in one embodiment;

[0044] Figure 9 This is a specific circuit diagram of the phase generator in one embodiment;

[0045] Figure 10 This is a logic timing diagram between signals in one embodiment;

[0046] Figure 11 This is a phase diagram of a buck-boost DC-DC converter in one embodiment.

[0047] Figure 12 This is a structural diagram of the third switching transistor in one embodiment.

[0048] Reference numerals: 100, voltage conversion module; 101, switching network; 110, voltage control module; 120, voltage input terminal; 130, voltage output terminal; 1101, compensation circuit; 1102, sawtooth wave generator; 1103, phase generator; 1104, drive signal generation circuit. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0050] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0051] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0052] Portable electronic devices are powered by lithium batteries, whose voltage gradually drops from 4.2V to 2.7V during use. Therefore, efficient multi-channel power supplies are required; typically, the display needs 3.4V, the I / O subsystem needs 1.8V, and the core processor needs 1V. Compared to traditional inductor converters, hybrid buck-boost converters built using flying capacitors generally have higher conversion efficiency. Common buck-boost DC-DC converters include multi-mode hybrid buck-boost DC-DC converters and single-mode large-inductor-current hybrid buck-boost converters, such as... Figure 1 The diagram shown is a circuit structure diagram of a multi-mode hybrid buck-boost DC-DC converter. Figure 2 The image shows a single-mode, high-inductance-current hybrid buck-boost converter. Multi-mode hybrid buck-boost DC-DC converters operate in two phases, meaning they have two operating states within a single duty cycle. One state allows for hard charging of the flying capacitor. However, with only one state for hard charging the flying capacitor, under extreme VCR (Voltage Conversion Ratio) conditions, the hard charging time may be too short, leading to large inrush currents, increased losses, and potential device damage. Furthermore, when the input and output voltages are close, the transition between de-energizing and boosting modes is not smooth, reducing circuit reliability. Additionally, the narrow voltage conversion ratio range prevents the conversion of lithium battery voltages to lower output voltages, such as 1.8V and 1V, thus limiting the application scenarios of buck-boost converters.

[0053] This application provides a buck-boost DC-DC converter, such as... Figure 3 The diagram shown is a circuit structure diagram of a buck-boost DC-DC converter. This buck-boost DC-DC converter may include a voltage input terminal 120, a voltage output terminal 130, and a voltage conversion module 100.

[0054] In this embodiment, the voltage input terminal 120 is connected to an external voltage source, and the input voltage output from the external voltage source is received through the voltage input terminal 120 as the energy source of the circuit. The voltage output terminal 130 can be connected to a load, and the converted voltage (i.e., the output voltage) is output to the load through the voltage output terminal 130. The voltage conversion module 100 includes a first flying capacitor CF1, a second flying capacitor CF2, an inductor L, and a switching network 101. One end of the first flying capacitor CF1 is connected to one end of the inductor L, and the connection node is connected to the voltage input terminal 120 and grounded through the switching network 101. The other end of the first flying capacitor CF1 is grounded and connected to the voltage input terminal 120 through the switching network 101. One end of the second flying capacitor CF2 is connected to the other end of the inductor L, and the connection node is connected to the voltage output terminal 130 through the switching network 101. The other end of the second flying capacitor CF2 is grounded and connected to the voltage output terminal 130 through the switching network 101. The switching network 101 is used to receive a drive signal and sequentially switch between a first state, a second state, and a third state in each switching cycle in response to the drive signal. In at least two of the first, second, and third states, the first flying capacitor CF1 and / or the second flying capacitor CF2 are connected in parallel with the inductor L to reduce the current on the inductor L.

[0055] In some embodiments, in the first state, the first flying capacitor CF1 and the second flying capacitor CF2 are connected in parallel with the inductor L, and the first flying capacitor CF1 and the second flying capacitor CF2 undergo hard charging; in the second state, the second flying capacitor CF2 is connected in parallel with the inductor L, and the second flying capacitor CF2 undergoes hard charging. Each switching cycle of the switching network 101 corresponds to one operating cycle of the buck-boost DC-DC converter. When the switching network 101 switches between the first state, the second state, and the third state, the buck-boost DC-DC converter is in different operating states, that is, the buck-boost DC-DC converter has three operating states in one operating cycle, and it is a three-phase operation. In the three operating states of the buck-boost DC-DC converter, the switching network 101 can hard charge the flying capacitors (first flying capacitor CF1 and / or second flying capacitor CF2) in two states. That is, in the two operating states of the buck-boost DC-DC converter, the flying capacitors (first flying capacitor CF1 and / or second flying capacitor CF2) can be hard charged, which prolongs the hard charging time. Under the condition of satisfying the ampere-second balance of the flying capacitors, large inrush currents are avoided on the first flying capacitor CF1 and the second flying capacitor CF2, reducing the current on the inductor L, reducing losses and protecting the device. In addition, the buck-boost DC-DC converter can continuously output current, thereby reducing the output voltage ripple.

[0056] In some embodiments, in the first state, the connection node of the first flying capacitor CF1 and the inductor L is connected to the voltage input terminal 120 through the switching network 101 and disconnected from ground. The other end of the first flying capacitor CF1 is grounded through the switching network 101 and disconnected from the voltage input terminal 120. The connection node of the second flying capacitor CF2 and the inductor L is connected to the voltage output terminal 130 through the switching network 101. The other end of the second flying capacitor CF2 is grounded through the switching network 101 and disconnected from the voltage output terminal 130. In the second state, the connection node of the first flying capacitor CF1 and the inductor L is disconnected from the voltage input terminal 120 and ground. The other end of the first flying capacitor CF1 is connected to the voltage output terminal 130 through the switching network 101. In the first state, the connection node of the first flying capacitor CF1 and inductor L is grounded through the switch network 101 and disconnected from the voltage input terminal 120. The other end of the first flying capacitor CF1 is disconnected from the voltage input terminal 120 and ground. The connection node of the second flying capacitor CF2 and inductor L is disconnected from the voltage output terminal 130. The other end of the second flying capacitor CF2 is connected to the voltage output terminal 130 through the switch network 101 and disconnected from the voltage output terminal 130.

[0057] like Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7As shown, in one embodiment, the switch network 101 may include a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, and a seventh switch S7. One end of the first switch S1 is connected to the voltage input terminal 120 and one end of the second switch S2, and the other end of the first switch S1 is connected to one end of the fourth switch S4, one end of the inductor L, and one end of the first flying capacitor CF1; the other end of the second switch S2 is connected to the other end of the first flying capacitor CF1 and one end of the third switch S3; one end of the fifth switch S5 is connected to the other end of the inductor L and one end of the second flying capacitor CF2; one end of the sixth switch S6 is connected to the other end of the second flying capacitor CF2 and one end of the seventh switch S7, and the other end of the sixth switch S6 is connected to the fifth switch S5 and the voltage output terminal 130; the other end of the third switch S3, the other end of the fourth switch S4, and the other end of the seventh switch S7 are connected to the voltage input terminal 120 and one end of the voltage output terminal 130; the other end of the third switch S3, the other end of the fourth switch S4, and the other end of the seventh switch S7 are connected to the voltage input terminal 120 and one end of the voltage output terminal 130. The other end of 7 is grounded; when the first switch S1, the third switch S3, the fifth switch S5, and the seventh switch S7 are in the on state, and the second switch S2, the fourth switch S4, and the sixth switch S6 are in the off state, the switch network 101 is in the first state; when the second switch S2, the fifth switch S5, and the seventh switch S7 are in the on state, and the first switch S1, the third switch S3, and the sixth switch S6 are in the off state, the switch network 101 is in the second state; when the fourth switch S4 and the sixth switch S6 are in the on state, and the first switch S1, the second switch S2, the third switch S3, the fifth switch S5, and the seventh switch S7 are in the off state, the switch network 101 is in the third state.

[0058] Specifically, the driving signals include a first driving signal, a second driving signal, and a third driving signal; wherein, the driving terminal of the first driving signal is connected to the control terminal of the first switch S1 and the control terminal of the third switch S3, and the first driving signal can control the conduction and turn-off of the first switch S1 and the third switch S3; the driving terminal of the second driving signal is connected to the control terminal of the second switch S2, the control terminal of the fourth switch S4, and the control terminal of the sixth switch S6, and the second driving signal can control the conduction and turn-off of the second switch S2, the fourth switch S4, and the sixth switch S6; the driving terminal of the third driving signal is connected to the control terminal of the fifth switch S5 and the control terminal of the seventh switch S7, and the third driving signal can control the conduction and turn-off of the fifth switch S5 and the seventh switch S7.

[0059] like Figure 4As shown, when the switch network 101 is in the first state, the first drive signal controls the first switch S1 and the third switch S3 to be in the on state; the second drive signal controls the second switch S2, the fourth switch S4 and the sixth switch S6 to be in the off state; the third drive signal controls the fifth switch S5 and the seventh switch S7 to be in the on state, and the first flying capacitor CF1 and the second flying capacitor CF2 are connected in parallel with the inductor L to perform hard charging.

[0060] like Figure 5 As shown, when the switch network 101 is in the second state, the first drive signal controls the first switch S1 and the third switch S3 to be in the off state; the second drive signal controls the second switch S2 to be in the on state, and controls the fourth switch S4 and the sixth switch S6 to be in the off state; the third drive signal controls the fifth switch S5 and the seventh switch S7 to be in the on state, the first flying capacitor CF1 and the inductor L are in series, the second flying capacitor CF2 is in parallel with the inductor L, and the second flying capacitor CF2 is hard charged.

[0061] like Figure 6 As shown, when the switch network 101 is in the third state, the first drive signal controls the first switch S1 and the third switch S3 to be in the off state; the second drive signal controls the second switch S2 to be in the off state and controls the fourth switch S4 and the sixth switch S6 to be in the on state; the third drive signal controls the fifth switch S5 and the seventh switch S7 to be in the off state, the first flying capacitor CF1 is set to float, and the second flying capacitor CF2 is connected in series with the inductor L.

[0062] In some embodiments, the duration of the first state is a preset duration. That is, under any circumstances, the duration of the first state is a preset duration, i.e., the conduction time of the first switch S1 and the third switch S3 within one switching cycle is a preset duration. Since the duration of the first state is a preset duration, the shortest duration during hard charging can be guaranteed. Therefore, the problem of short hard charging time under extreme VCR conditions is further avoided. That is, the problem of short hard charging time under extreme VCR conditions can be avoided by setting a fixed value.

[0063] In some embodiments, the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, and the seventh switch S7 are all transistors. The transistors can be any of the following: N-MOS (N-channel Metal-Oxide-Semiconductor Field-Effect Transistor), P-MOS (P-channel Metal-Oxide-Semiconductor Field-Effect Transistor), or bipolar transistors. Those skilled in the art can determine the specific types of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, and the seventh switch S7 according to the actual situation.

[0064] In one specific embodiment, the second switch S2, the fourth switch S4, the fifth switch S5, the sixth switch S6, and the seventh switch S7 are N-MOS transistors. The gate of the second switch S2 is the control terminal of the second switch S2; the gates of the fourth switch S4, the fifth switch S5, and the sixth switch S6 are all control terminals of the fourth switch S4; the gate of the seventh switch S7 is also the control terminal of the seventh switch S7. The drain of the second switch S2 is connected to the voltage input terminal 120, and the source is connected to the first flying capacitor CF1; the source of the fourth switch S4 is grounded, and the drain is connected to the inductor L; the drain of the fifth switch S5 is connected to the inductor L, and the source is connected to the voltage output terminal 130; the source of the sixth switch S6 is connected to the second flying capacitor CF2, and the drain is connected to the voltage output terminal 130; the source of the seventh switch S7 is grounded, and the drain is connected to the second flying capacitor CF2.

[0065] In some embodiments, both the first switch S1 and the third switch S3 are MOS transistors that integrate a dynamic body selector. In one specific embodiment, both the first switch S1 and the third switch S3 are N-MOS transistors that integrate a dynamic body selector.

[0066] In this embodiment, to avoid leakage current in the body diode, the low-voltage ends of the first switch S1 and the third switch S3 are used as the source, and the high-voltage ends are used as the drain. The source of the first switch S1 is connected to its substrate, and the source of the third switch S3 is also connected to its substrate. When the switching network 101 is in the second state and the third state, the source and drain of the third switch S3 will switch. Specifically, in the second state, VZ = VIN, the VZ terminal is the drain of the third switch S3, and the grounded end of the third switch S3 is its source; in the third state, the VZ terminal is the source of the third switch S3, and the grounded end of the third switch S3 is its drain.

[0067] like Figure 12 The diagram shows the structure of the third switch S3. The third switch S3 integrates a Dynamic Body Terminal Selector (DBTS). When the switch network 101 is in the second state, GND is low and VZ is high, turning on switch Sa2 and turning off switch Sa1. The substrate of the third switch S3 is connected to ground, and the grounded end of the third switch S3 serves as its source. When the switch network 101 is in the third state, the grounded end of the third switch S3 is high, and the end connected to VZ is low. Switch Sa2 is off, and switch Sa1 is on. The substrate of the third switch S3 is connected to the end connected to VZ, and the VZ-connected end serves as its source.

[0068] In some embodiments, such as Figure 7 As shown, the step-up / step-down DC-DC converter also includes a voltage control module 110, which is connected to the voltage output terminal 130 and the switching network 101. The voltage control module 110 is used to generate a drive signal according to the output voltage and a preset reference voltage, so that the switching network 101 sequentially switches between a first state, a second state and a third state in each switching cycle, and the first state lasts for a preset duration.

[0069] Specifically, such as Figure 7As shown, the voltage control module 110 may include a compensation circuit 1101, a sawtooth wave generator 1102, a first comparator MP1, a second comparator MP2, a three-phase generator 1103, and a drive signal generation circuit 1104. The input terminal of the compensation circuit 1101 is connected to the voltage output terminal 130 and is used to amplify the output voltage and compensate for its frequency to generate a first voltage signal. The sawtooth wave generator 1102 generates a sawtooth wave signal and a clock signal. The first comparator MP1 acquires the sawtooth wave signal and a preset reference voltage, generating a first comparison signal characterizing the comparison result between the sawtooth wave signal and the preset reference voltage. The second comparator MP2 acquires the first voltage signal and the sawtooth wave signal, generating a second comparison signal characterizing the comparison result between the sawtooth wave signal and the first voltage signal. The phase generator 1103 receives the first comparison signal, the second comparison signal, and the clock signal to generate a reference clock signal, and outputs it to the drive signal generation circuit 1104. The drive signal generation circuit 1104 generates a drive signal in response to the reference clock signal.

[0070] like Figure 7 As shown, the compensation circuit 1101 is a three-type compensation circuit 1101. The three-type compensation circuit 1101 can generate a first voltage signal after error amplification and frequency compensation of the output voltage of the voltage output terminal 130, and output it to the inverting input terminal of the first comparator MP1.

[0071] In practical applications, the first reference voltage V output by the reference source is set. D1 (i.e., preset reference voltage), first reference voltage V D1 The first voltage signal V output by the type-three compensation circuit 1101 is less than three times the voltage signal V. EA In the initial stage, the sawtooth wave signal V output by the sawtooth wave generator 1102 RAMP Starting from the lowest point, the voltage signal C output by the first comparator MP1 rises. MPVD1 The voltage signal C output by the second comparator MP2 MPVEA All are low-level signals. For example... Figure 8 , Figure 9As shown, the sawtooth wave generator 1102 also generates a clock signal CLK, which is fed into the S terminal of the RS latch in the phase generator 1103. The RS latch output signal Q1 is high, and Q2 and Q3 are low. The output signals Q1, Q2, and Q3 are input to the digital logic module of the phase generator 1103, and are converted into gate voltage control signals Pre-D1, Pre-D2, and Pre-D3 (i.e., Pre-D1, Pre-D2, and Pre-D3 are reference control signals) controlling the gate voltages of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, and the seventh switch S7. At this time, Pre-D1 is high, and Pre-D2 and Pre-D3 are low. After passing through the drive signal generation circuit 1104, Pre-D1, Pre-D2, and Pre-D3 generate the first drive signal. The first drive signal turns on the first switch S1 and the third switch S3, the second drive signal turns off the second switch S2, the fourth switch S4 and the sixth switch S6, and the third drive signal turns on the fifth switch S5 and the seventh switch S7. The switching network 101 is in the first state. The first flying capacitor CF1 and the inductor L are connected in parallel. The input voltage hard charges the first flying capacitor CF1 through the first switch S1 and the third switch S3, and the voltage on the first flying capacitor CF1 is charged to VCF1=VIN. The second flying capacitor CF2 and the inductor L are connected in parallel. The output voltage hard charges the second flying capacitor CF2 through the fifth switch S5 and the seventh switch S7, and the voltage on the second flying capacitor CF2 is charged to VCF2=VOUT. At the same time, a voltage difference of VIN-VOUT is formed on the inductor L. Figure 7 In the diagram, D1 represents the first drive signal; D2 represents the second drive signal; and ND3 represents the third drive signal.

[0072] During the rise of the sawtooth wave signal output by the sawtooth wave generator 1102, due to the first reference voltage V... D1 The first voltage signal V output by the type-three compensation circuit 1101 is less than three times the voltage signal V. EA First, with the first reference voltage V D1 Intersecting, in the sawtooth wave signal V RAMP With the first reference voltage V EAWhen the phases intersect, the output signal of the first comparator MP1 is high, the R terminal of the RS latch in the phase generator 1103 is set to high, the output signal Q1 is low, and when the D flip-flop receives the edge trigger signal, the output signal Q2 is high, while the output signal Q3 remains low. After the output signals Q1, Q2, and Q3 enter the digital logic module in the phase generator 1103, they are converted into gate voltage control signals Pre-D1, Pre-D2, and Pre-D3 to control the gate voltages of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, and the seventh switch S7. Control signals Pre-D1 are low, Pre-D2 is high, and Pre-D3 is low. Pre-D1, Pre-D2, and Pre-D3 then pass through the drive signal generation circuit 1104. A first drive signal, a second drive signal, and a third drive signal are generated. The first drive signal controls the first switch S1 and the third switch S3 to be in the off state; the second drive signal controls the second switch S2 to be in the on state and controls the fourth switch S4 and the sixth switch S6 to be in the off state; the third drive signal controls the fifth switch S5 and the seventh switch S7 to be in the on state. The first flying capacitor CF1 and the inductor L are in series, and the second flying capacitor CF2 is in parallel with the inductor L. The second flying capacitor CF2 is hard-charged; the switching network 101 is in the second state. In the second state, the second switch S2, the fifth switch S5, and the seventh switch S7 are in the on state, while the other switches are in the off state. A voltage difference of 2VIN-VOUT is formed across the inductor L, causing the inductor current to rise at a slope of (2VIN-VOUT) / L. The first flying capacitor CF1 is connected in series with the inductor L and discharges to the voltage output terminal 130. The second flying capacitor CF2 is kept in parallel with the inductor L and in parallel with the output capacitor COUT, maintaining its voltage value as VOUT. The output voltage is collected and enters the three-type compensation circuit 1101 of the voltage control module 110. After error amplification and frequency compensation with the second reference voltage VREF through the three-type compensation circuit 1101, the error amplifier output voltage VEA is generated.When VRAMP rises to intersect with VEA, the output signal of the second comparator MP2 is high, the D flip-flop D1 in the phase generator 1103 is reset, and the output signal Q2 outputs low. The second D flip-flop receives the edge trigger signal, causing the output signal Q3 to output high. The output signal Q1 remains low until the next CLK arrives. After the output signals Q1, Q2, and Q3 enter the digital logic module of the phase generator 1103, the output control signals Pre-D1 are low, Pre-D2 are low, and Pre-D3 are high, controlling... Signals Pre-D1, Pre-D2, and Pre-D3 are processed by the drive signal generation circuit 1104 to generate a first drive signal, a second drive signal, and a third drive signal. The first drive signal controls the first switch S1 and the third switch S3 to be in the off state; the second drive signal controls the second switch S2 to be in the off state and controls the fourth switch S4 and the sixth switch S6 to be in the on state; the third drive signal controls the fifth switch S5 and the seventh switch S7 to be in the off state. The first flying capacitor CF1 is set to float, and the second flying capacitor CF2 is connected in series with the inductor L. In the third state, the switching network 101 forms a voltage difference of -2VOUT across the inductor L, causing the inductor current to decrease at a slope of -2VOUT / L. The second flying capacitor CF2 is connected in series with the inductor L and discharges to the voltage output terminal 130. When one cycle ends, the clock signal CLK output by the sawtooth wave generator 1102 is input into the phase generator 1103, and the sawtooth wave signal V... RAMP The voltage immediately drops to the lowest level and begins to rise again; the switching network 101 recharges to the first state and begins switching. Figure 10 The diagram shown is a timing logic diagram between signals.

[0073] The buck-boost DC-DC converter operates in buck mode when the input voltage at voltage input terminal 120 is greater than the output voltage at voltage output terminal 130; conversely, it operates in boost mode when the input voltage at voltage input terminal 120 is less than the output voltage at voltage output terminal 130. In the first state, the switching network 101 causes the inductor L current to increase with a slope of (VIN-VOUT) / L in buck mode and decreases with a slope of (VOUT-VIN) / L in boost mode.

[0074] Since the switching network 101 switches from the first state to the second state after the sawtooth wave signal intersects with the first reference voltage, the duration of the first state, i.e., the preset duration of the first state, can be determined by setting a specific value of the first reference voltage. In this embodiment, by setting the first reference voltage, the duration of the first state is 0.3 TS, that is, the first drive signal causes the first switch S1 and the third switch S3 to be on for 0.3 TS. Of course, those skilled in the art can also set the duration to other values ​​according to actual needs, such as 0.4 TS or 0.45 TS.

[0075] In this embodiment, the voltage control module 110 in the buck-boost DC-DC converter controls the switching transistors in the switching network 101 to make the first flying capacitor CF1 bear the output voltage of the voltage input terminal 120 and the second flying capacitor CF2 bear the output voltage of the voltage output terminal 130, so that the voltages VIN, 2VIN and 0 alternately appear at the node VX where the inductor L is connected to the first switching transistor S1; Figure 11 As shown, the node VY connecting inductor L and the fifth switch S5 alternately displays voltages VOUT, VOUT, and 2VOUT, where VIN, 2VIN, and 0 have durations of D1T. S D2T S and (1-D1-D2)T S VOUT, VOUT, and 2VOUT have durations of D1T respectively. S D2T S and (1-D1-D2)T S Among them, D1T S With a fixed phase, the surge current on inductor L and the ripple of the output voltage can be effectively reduced, and the first flying capacitor CF1 and the second flying capacitor CF2 are ensured to have a minimum hard charging time, thus reducing the surge current of the flying capacitors. D2 is the duty cycle modulated by the voltage control module 110, T S For the switching cycle, according to the inductor volt-second balance rule, the voltage conversion ratio (VCR) of this buck-boost DC-DC converter is:

[0076] ;

[0077] in, The output voltage at voltage output terminal 130; The input voltage at voltage input terminal 120; The duty cycle in the first state; This represents the duty cycle in the second state.

[0078] Therefore, the voltage conversion ratio can be adjusted by adjusting D1, thus this buck-boost DC-DC converter has a wider range of voltage conversion ratios.

[0079] From the perspective of current conduction, the average circuit undertaken by inductor L is:

[0080] ;

[0081] in, This is the load current; This represents the average current carried by the inductor L.

[0082] Since the sum of D1+D2 is less than 1, the current in inductor L is always less than the current in the load, which reduces the current value in inductor L and reduces the conduction loss in DCR (Direct Current Resistance).

[0083] In this embodiment, the average current provided by the first flying capacitor CF1 during hard charging is:

[0084] ;

[0085] in, The average current provided for the first flying capacitor CF1.

[0086] The average current provided by the second capacitor CF2 during hard charging is:

[0087] ;

[0088] in, The average current provided for the second flying capacitor CF2.

[0089] Since conduction loss is proportional to the square of the current (current flowing through the flying capacitor), the conduction loss of the power inductor is greatly reduced, and no large surge current will appear on the flying capacitors CF1 and CF2, avoiding circuit overheating and device damage, thus improving reliability.

[0090] In some embodiments, the voltage conversion module further includes an output capacitor connected between the voltage output terminal 130 and ground to stabilize the output voltage. Specifically, one end of the output capacitor is connected to the voltage output terminal 130, and the other end of the output capacitor is grounded. The output capacitor enables the voltage output terminal 130 to stabilize the output voltage, that is, to stabilize the output target voltage.

[0091] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A step-up / step-down DC-DC converter, characterized in that, include: The voltage input terminal is used to connect the input voltage output from an external voltage source; The voltage output terminal is used to provide the output voltage to the connected load. The voltage conversion module includes a first flying capacitor, a second flying capacitor, an inductor, and a switching network; One end of the first flying capacitor is connected to one end of the inductor, and the connection node is connected to the voltage input terminal and grounded through the switching network. The other end of the first flying capacitor is grounded and connected to the voltage input terminal through the switching network. One end of the second flying capacitor is connected to the other end of the inductor, and the connection node is connected to the voltage output terminal through the switching network. The other end of the second flying capacitor is grounded and connected to the voltage output terminal through the switching network. The switching network is used to receive a drive signal and, in response to the drive signal, sequentially switch between a first state, a second state, and a third state in each switching cycle; in at least two of the first state, the second state, and the third state, the first flying capacitor and / or the second flying capacitor are connected in parallel with the inductor to reduce the current on the inductor.

2. The step-up / step-down DC-DC converter as described in claim 1, characterized in that, In the first state, the connection node of the first flying capacitor and the inductor is connected to the voltage input terminal through the switching network and disconnected from ground. The other end of the first flying capacitor is grounded through the switching network and disconnected from the voltage input terminal. The connection node of the second flying capacitor and the inductor is connected to the voltage output terminal through the switching network. The other end of the second flying capacitor is grounded through the switching network and disconnected from the voltage output terminal. In the second state, the connection node of the first flying capacitor and the inductor is disconnected from the voltage input terminal and ground. The other end of the first flying capacitor is connected to the voltage input terminal through the switching network and disconnected from ground. The connection node of the second flying capacitor and the inductor is connected to the voltage output terminal through the switching network. The other end of the second flying capacitor is grounded through the switching network and disconnected from the voltage output terminal. In the third state, the connection node of the first flying capacitor and the inductor is grounded through the switching network and disconnected from the voltage input terminal. The other end of the first flying capacitor is disconnected from the voltage input terminal and ground. The connection node of the second flying capacitor and the inductor is disconnected from the voltage output terminal. The other end of the second flying capacitor is connected to the voltage output terminal through the switching network and disconnected from ground.

3. The step-up / step-down DC-DC converter as described in claim 2, characterized in that, The first state lasts for a preset duration.

4. The step-up / step-down DC-DC converter as described in any one of claims 1-3, characterized in that, The switching network includes: a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, and a seventh switch; One end of the first switch is connected to the voltage input terminal and one end of the second switch; the other end of the first switch is connected to one end of the fourth switch, one end of the inductor, and one end of the first flying capacitor; the other end of the second switch is connected to the other end of the first flying capacitor and one end of the third switch; one end of the fifth switch is connected to the other end of the inductor and one end of the second flying capacitor; one end of the sixth switch is connected to the other end of the second flying capacitor and one end of the seventh switch; the other end of the sixth switch is connected to the fifth switch and the voltage output terminal; the other ends of the third switch, the fourth switch, and the seventh switch are grounded. When the first switch, the third switch, the fifth switch, and the seventh switch are in the ON state, and the second switch, the fourth switch, and the sixth switch are in the OFF state, the switch network is in the first state; When the second switch, the fifth switch, and the seventh switch are in the ON state, and the first switch, the third switch, and the sixth switch are in the OFF state, the switch network is in the second state; When the fourth and sixth switches are in the ON state, and the first, second, third, fifth, and seventh switches are in the OFF state, the switch network is in the third state.

5. The step-up / step-down DC-DC converter as described in claim 4, characterized in that, The second switch, the fourth switch, the fifth switch, the sixth switch, and the seventh switch are all transistors.

6. The step-up / step-down DC-DC converter as described in claim 5, characterized in that, The first and third switching transistors are MOS transistors with integrated dynamic body selectors.

7. The buck-boost DC-DC converter as described in claim 4, characterized in that, The buck-boost DC-DC converter also includes: A voltage control module is connected to the voltage output terminal and the switching network. The voltage control module is used to generate the drive signal according to the output voltage and the preset reference voltage, so that the switching network sequentially switches the first state, the second state and the third state in each switching cycle, and the first state lasts for the preset duration.

8. The step-up / step-down DC-DC converter as described in claim 7, characterized in that, The voltage control module includes: a compensation circuit, a sawtooth wave generator, a first comparator, a second comparator, a three-phase generator, and a drive signal generation circuit; The input terminal of the compensation circuit is connected to the voltage output terminal, and is used to amplify the output voltage and compensate for the frequency to generate a first voltage signal. The sawtooth wave generator is used to generate sawtooth wave signals and clock signals; The first comparator is used to acquire the sawtooth wave signal and the preset reference voltage, and generate a first comparison signal characterizing the comparison result between the sawtooth wave signal and the preset reference voltage; The second comparator is used to acquire the first voltage signal and the sawtooth wave signal, and generate a second comparison signal characterizing the comparison result between the sawtooth wave signal and the first voltage signal; The phase generator is used to receive the first comparison signal, the second comparison signal and the clock signal to generate a reference clock signal and output it to the drive signal generation circuit; The drive signal generation circuit is used to generate the drive signal in response to the reference clock signal.

9. The step-up / step-down DC-DC converter as described in claim 8, characterized in that, The compensation circuit is a type III compensation circuit.

10. The buck-boost DC-DC converter as described in claim 1 or 2, characterized in that, The voltage conversion module also includes: An output capacitor is connected between the voltage output terminal and ground to stabilize the output voltage.

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